Conditioned craving cues elicit an automatic approach tendency

The effects of a retrieval cue on renewal of conditioned responses in human appetitive conditioning

Contextual renewal of reward anticipation may be one potential mechanism underlying relapse in eating and substance use disorders. We therefore tested retrieval cues, a method derived from an inhibitory retrieval-based model of extinction learning to attenuate contextual renewal using an appetitive conditioning paradigm. A pilot study was carried out in Experiment 1 to validate a differential chocolate conditioning paradigm, in which a specific tray was set up as a conditioned stimulus (CS) for eating chocolate (unconditioned stimulus, US). Using an ABA renewal design in Experiment 2, half of the participants were presented with a retrieval cue in the acquisition phase (group AC) and the other half in the extinction phase (group EC). Presentation of the retrieval cue in the EC was associated with reduced renewal of US-expectancy, while there was a clear renewal effect for US-expectancy in the AC. One limitation was the difference in cue presentations between both groups due to the number of trials in acquisition and extinction. Experiment 3 therefore aimed at replicating the results of Experiment 2, but with fewer cue presentations for the EC to match the AC. No significant group differences were observed indicating no effect of the retrieval cue. Theoretical and clinical implications in light of the differing results are discussed.

Imagine chocolate: The craving experience questionnaire in the food domain

Measurement of food craving has gained relevance in the current obesity epidemic. The Craving Experience Questionnaire (CEQ) considers not only craving intensity but also cognitive intrusiveness and imagery vividness as separate craving factors and could thus refine food craving assessment. It is available in two versions with ten items each. The CEQ-F assesses craving frequency across specific time periods and the CEQ-S time-point specific craving strength. Across three independent studies, N = 533 participants completed the German chocolate CEQ-F referenced at the past year to operationalise trait-like craving. Among them, N = 402 also completed the German chocolate CEQ-S referenced at the current moment to operationalise state-like craving. Four-week test-retest reliability was measured. For external validity, we assessed self-reported chocolate consumption, body-mass-index, trait approach motivation, general imagery vividness, and the most widely used food craving questionnaire, namely the Food Cravings Questionnaires in a trait (FCQ-T-r) and state version (FCQ-S), as well as behavioural approach bias (reaction time-based measurement). The three-factor structure was replicated with excellent internal consistency for both CEQ-F and CEQ-S. Test-retest reliability was moderate for both CEQ versions. CEQ-F scores were related to higher levels of chocolate consumption, approach motivation, and FCQ-T-r scores, but not to body-mass-index, imagery vividness, or approach bias. CEQ-S scores were associated with FCQ-S scores and partly with approach bias, but not with approach motivation and imagery vividness. The current results support the factor structure, validity and reliability of the German chocolate CEQ-S and CEQ-F with questions remaining regarding the ability of the CEQ-S to measure state craving. Thus, CEQ-F and CEQ-S usefully contribute to food craving assessment.

The Impact of Modifiable Preoral Factors on Swallowing and Nutritional Outcomes in Healthy Adults: A Scoping Review

PURPOSE

Swallowing has previously been characterized as consisting of four phases; however, it has become apparent that these four phases are not truly discrete and may be influenced by factors occurring prior to bolus entrance into the oral cavity (i.e., preoral factors). Still, the relationship between these factors and swallowing remains poorly understood. The aim of this review was to synthesize and characterize the literature pertaining to the influence of preoral factors on swallowing and nutritional outcomes in healthy individuals.

METHOD

We performed a scoping review, searching the databases of PubMed, CINAHL, Cochrane, and Scopus. Search terms included those related to swallowing, experience of preoral factors, and exclusionary terminology to reduce animal and pediatric literature. Our initial search revealed 5,560 unique articles, of which 153 met our inclusionary criteria and were accepted into the review.

RESULTS

Of the accepted articles, 78% were focused exclusively on nutritional outcomes, 17% were focused on both swallowing and nutritional outcomes, and 5% were focused on solely swallowing outcomes. Of the preoral factors examined, 99% were exteroceptive in nature (17% olfactory, 44% visual, 21% auditory, 7% tactile, 11% other), while 1% were proprioceptive in nature.

CONCLUSIONS

This review supports the influence of preoral factors on swallowing and nutritional outcomes. However, there is a large emphasis on the visual modality and on nutritional outcomes. Nearly none of the literature found in this review directly measured swallowing safety, efficiency, or physiology. Future work will benefit from a larger focus on proprioceptive preoral factors as they relate to swallowing outcomes.

Modifying Pavlovian-to-instrumental transfer by approach avoidance training in healthy subjects: a proof of concept study

The modulation of instrumental action by conditioned Pavlovian cues is hypothesized to play a role in the emergence and maintenance of maladaptive behavior. The Pavlovian to Instrumental transfer task (PIT) is designed to examine the magnitude of the influence of cues on behavior and we aim to manipulate the motivational value of Pavlovian cues to reduce their effect on instrumental responding. To this end, we utilized a joystick-based modification of approach and avoidance propensities that has shown success in clinical populations. To examine changes in PIT, we subjected 35 healthy participants to a series of experimental procedures: (1) Instrumental training was followed by (2) Pavlovian conditioning of neutral stimuli that were associated with monetary reward or loss. (3) In a subsequent joystick task, approach and avoidance tendencies toward conditioned cues were assessed. (4) In a transfer test, the PIT effect as the impact of conditioned cues on instrumental behavior was measured. (5) The explicit knowledge of cue-reward contingencies was assessed in a forced-choice phase. (6, 7) systematic joystick training was followed by a posttest (8) the transfer task and forced-choice test were repeated. We found no effect of training on approach-avoidance propensities in the context of this proof of concept study. A higher response rate towards negative stimuli during PIT after systematic training compared to sham training was seen. On the other hand, we saw an increased PIT effect after sham training. These results contribute to the understanding of the strength of the influence of cues on instrumental behavior. Our findings further stress the importance of context, instructions and operationalization of instrumental behavior in the framework of transfer effects.

The Influence of Sexual Arousal on Self-Reported Sexual Willingness and Automatic Approach to Models of Low, Medium, and High Prior Attractiveness

Anecdotal evidence suggests that sexual attraction is flexible, and that high levels of sexual arousal can promote sexual willingness and approach tendencies toward a priori low attractive mates. This experimental study tested whether heightened sexual arousal can lower the threshold for sexual willingness and automatic approach tendencies toward potential sex partners of low and medium attractiveness. Heterosexual male (n =54) and female (n =61) participants were randomly assigned to a sexual arousal or control condition. Approach tendencies were indexed using a reaction time task. Sexual willingness was indexed using participant ratings of willingness to kiss and to consider having sex with same- and other-sex models of low, medium, and high attractiveness. Overall, participants showed stronger approach to models of high and medium than of low attractiveness. Sexual arousal weakened this differential responding but did not result in a robust increase of approach toward less attractive other-sex or same-sex models. Sexual willingness toward less attractive models was not affected by sexual arousal. Independent of condition, women reported greater sexual willingness toward same-sex models. The current pattern of findings does not support the notion that sexual arousal promotes automatic approach and sexual willingness to a broader array of sex partners.

Regulating food craving: From mechanisms to interventions

Craving, defined here as a strong desire to eat, is a common experience that drives behavior. Here we discuss the concept of craving from historical, physiological, and clinical perspectives, and review work investigating the effects of cue reactivity and cue-induced craving on eating and weight outcomes, as well as underlying neural mechanisms. We also highlight the significance of cue reactivity and craving in the context of our "toxic food environment" and the obesity epidemic. We then summarize our work developing the Regulation of Craving (ROC) task, used to test the causal effects of cognitive strategies on craving for food and drugs as well as the underlying neural mechanisms of such regulation. Next, we review our recent development of a novel ROC-based intervention that trains individuals to use cognitive strategies to regulate craving, with promising effects on subsequent food choice and caloric consumption. We end by discussing future directions for this important line of work.

From sign-tracking to attentional bias: Implications for gambling and substance use disorders

Sign-tracking behavior in Pavlovian autoshaping is known to be a relevant index of the incentive salience attributed to reward-related cues. Evidence has accumulated to suggest that animals that exhibit a sign-tracker phenotype are especially vulnerable to addiction and relapse due to their proneness to attribute incentive salience to drug cues, and their relatively weak cognitive and attentional control over their behavior. Interestingly, sign-tracking is also influenced by reward uncertainty in a way that may promote gambling disorder. Research indicates that reward uncertainty sensitizes sign-tracking responses and favors the development of a sign-tracker phenotype, compatible with the conditioned attractiveness of lights and sounds in casinos for problem gamblers. The study of attentional biases in humans (an effect akin to sign-tracking in animals) leads to similar observations, notably that the propensity to develop attraction for conditioned stimuli (CSs) is predictive of addictive behavior. Here we review the literature on drug addiction and gambling disorder, highlighting the similarities between studies of sign-tracking and attentional biases.

The Reciprocal Relationship Between Sexual Arousal and Disgust as Evidenced in Automatic Approach-Avoidance Behavior

Sexual encounters imply exposure to stimuli that in other contexts typically elicit disgust-induced avoidance. To explain why people nevertheless tend to show sexual approach, it has been proposed that heightened sexual arousal may temporarily inhibit disgust. In line with this, studies have found that sexually aroused individuals showed heightened willingness to approach disgusting stimuli. Because automatic processes are critically involved in sexual behaviors, we examined whether the impact of sexual arousal extends to automatic responses to disgust-elicitors. To test the proposed reciprocal relationship between sex and disgust, we also investigated whether disgust reduces automatic sexual approach. In Study 1, 116 female participants (M = age 19.53) were assigned to a sexual arousal or control condition and performed a speeded approach-avoidance task to assess automatic responses to disgusting stimuli. In Study 2, 174 female participants (M = age 22.14) were assigned to a disgust, sexual arousal, or control condition and performed an approach-avoidance task involving both sex and disgust-relevant stimuli. Sexual arousal did not affect automatic responses to disgusting stimuli, and disgust did not influence automatic responses towards sexual stimuli. The reciprocal relationship between sexual arousal and disgust that was previously found for controllable responses did not extend to automatic responses.

An experimental study on spontaneous recovery of conditioned reward expectancies and instrumental responding in humans

The aim of the present study was to investigate spontaneous recovery of reward-expectancies and a reward-associated response in humans and to assess individual factors affecting spontaneous recovery. We therefore implemented an experimental procedure comprising three separate test-sessions. In the first test-session, participants underwent instrumental discrimination training to acquire a conditioned reward-associated response, in the second test-session, memory of this response was tested followed by extinction training. In the third test-session, extinction memory was assessed. Our results demonstrate spontaneous recovery of extinguished conditioned reward-associated expectancies and indicate that differential expectancies after training and extinction and impulsivity significantly predicted the magnitude of spontaneous recovery. In contrast, limited evidence for spontaneous recovery of instrumental responding was found. Given that reward-expectancies might trigger instrumental responding these findings underline the importance of developing extinction procedures that lead to more complete and less fragile long-term extinction of reward-associated responses.

Learned Overeating: Applying Principles of Pavlovian Conditioning to Explain and Treat Overeating

PURPOSE OF REVIEW

This review provides an overview of recent findings relating to the role of Pavlovian conditioning in food cue reactivity, including its application to overeating and weight loss interventions.

RECENT FINDINGS

Both in the laboratory and in real life, cue-elicited appetitive reactivity (e.g., eating desires) can be easily learned, but (long-term) extinction is more difficult. New findings suggest impaired appetitive learning in obesity, which might be causally related to overeating. The clinical analogue of extinction-cue exposure therapy-effectively reduces cue-elicited cravings and overeating. While its working mechanisms are still unclear, some studies suggest that reducing overeating expectancies is important.

SUMMARY

Pavlovian learning theory provides a still undervalued theoretical framework of how cravings and overeating can be learned and how they might be effectively tackled. Future studies should aim to elucidate inter-individual differences in Pavlovian conditioning, study ways to strengthen (long-term) extinction, and investigate the working mechanisms of cue exposure therapy.

Measuring Pavlovian appetitive conditioning in humans with the postauricular reflex

Despite its evolutionary and clinical significance, appetitive conditioning has been rarely investigated in humans. It has been proposed that this discrepancy might stem from the difficulty in finding suitable appetitive stimuli that elicit strong physiological responses. However, this might also be due to a possible lack of sensitivity of the psychophysiological measures commonly used to index human appetitive conditioning. Here, we investigated whether the postauricular reflex—a vestigial muscle microreflex that is potentiated by pleasant stimuli relative to neutral and unpleasant stimuli—may provide a valid psychophysiological indicator of appetitive conditioning in humans. To this end, we used a delay differential appetitive conditioning procedure, in which a neutral stimulus was contingently paired with a pleasant odor (CS+), while another neutral stimulus was not associated with any odor (CS−). We measured the postauricular reflex, the startle eyeblink reflex, and skin conductance response (SCR) as learning indices. Taken together, our results indicate that the postauricular reflex was potentiated in response to the CS+ compared with the CS−, whereas this potentiation extinguished when the pleasant odor was no longer delivered. In contrast, we found no evidence for startle eyeblink reflex attenuation in response to the CS+ relative to the CS−, and no effect of appetitive conditioning was observed on SCR. These findings suggest that the postauricular reflex is a sensitive measure of human appetitive conditioning and constitutes a valuable tool for further shedding light on the basic mechanisms underlying emotional learning in humans.

Measuring appetitive conditioned responses in humans

Clinical and preclinical findings suggest that individuals with abnormal responses to reward cues (stimuli associated with reward) may be at risk for maladaptive behaviors including obesity, addiction and depression. Our objective was to develop a new paradigm for producing appetitive conditioning using primary (food) rewards in humans, and investigate the equivalency of several outcomes previously used to measure appetitive responses to conditioned cues. We used an individualized food reward, and multimodal subjective, psychophysiological and behavioral measures of appetitive responses to a conditioned stimulus (CS) that predicted delivery of that food. We tested convergence among these measures of appetitive response, and relationships between these measures and action impulsivity, a putative correlate of appetitive conditioning. 90 healthy young adults participated. Although the paradigm produced robust appetitive conditioning in some measures, particularly psychophysiological ones, there were not strong correlations among measures of appetitive responses to the CS, as would be expected if they indexed a single underlying process. In addition, there was only one measure that related to impulsivity. These results provide important information for translational researchers interested in appetitive conditioning, suggesting that various measures of appetitive conditioning cannot be treated interchangeably.

Altered appetitive conditioning in overweight and obese women

Overweight and obese individuals show increased psychological and physiological reactivity to food cues and many of them have difficulties in achieving long-term weight loss. The current study tests whether abnormalities in the learning and extinction of appetitive responses to food cues might be responsible for this. Overweight/obese and healthy weight women completed a differential appetitive conditioning task using food as rewards, while eating expectancies, eating desires, conditioned stimulus evaluations, salivation, and electrodermal responses were assessed during an acquisition and extinction phase. Results suggested reduced discriminative conditioning in the overweight/obese group, as reflected by a worse acquisition of differential eating desires and no successful acquisition of differential evaluative responses. Some evidence was also found for impaired contingency learning in overweight and obese individuals. No group differences in conditioned salivation and skin conductance responses were found and no compelling evidence for differences in extinction was found as well. In sum, the current findings indicate that overweight and obesity may be characterized by reduced appetitive conditioning. It is suggested that this could be causally related to overeating via stronger context conditioning or a tendency towards overgeneralization in overweight and obese individuals.

Memory Reconsolidation Interference as an Emerging Treatment for Emotional Disorders: Strengths, Limitations, Challenges, and Opportunities

Experimental research on emotional memory reconsolidation interference, or the induction of amnesia for previously established emotional memory, has a long tradition, but the potential of that research for the development of novel interventions to treat psychological disorders has been recognized only recently. Here we provide an overview of basic research and clinical studies on emotional memory reconsolidation interference. We point out specific advantages of interventions based on memory reconsolidation interference over traditional treatment for emotional disorders. We also explain how findings from basic research suggest limitations and challenges to clinical translation that may help to understand why clinical trials have met with mixed success so far and how their success can be increased. In closing, we preview new intervention approaches beyond the induction of amnesia that the phenomenon of memory reconsolidation may afford for alleviating the burden imposed by emotional memories and comment on theoretical controversies regarding the nature of memory reconsolidation.

The Pavlovian craver: Neural and experiential correlates of single trial naturalistic food conditioning in humans

Present-day environments are replete with tempting foods and the current obesity pandemic speaks to humans' inability to adjust to this. Pavlovian processes may be fundamental to such hedonic overeating. However, a lack of naturalistic Pavlovian paradigms in humans makes translational research difficult and important parameters such as implicitness and acquisition speed are unknown. Here we present a novel naturalistic conditioning task: an image of a neutral object was conditioned to marzipan taste in a single trial procedure by asking the participant to eat the 'object' (made from marzipan). Relative to control objects, results demonstrate robust pre- to post-conditioning changes of both subjective ratings and early as well as late event related brain potentials, suggesting contributions of implicit (attentional) and explicit (motivational) processes. Naturalistic single-trial taste-appetitive conditioning is potent in humans and shapes attentional and motivational neural processes that might challenge self-regulation during exposure to tempting foods. Thus, appetitive conditioning processes might contribute to overweight and obesity.

Food cue reactivity and craving predict eating and weight gain: a meta-analytic review

According to learning-based models of behavior, food cue reactivity and craving are conditioned responses that lead to increased eating and subsequent weight gain. However, evidence supporting this relationship has been mixed. We conducted a quantitative meta-analysis to assess the predictive effects of food cue reactivity and craving on eating and weight-related outcomes. Across 69 reported statistics from 45 published reports representing 3,292 participants, we found an overall medium effect of food cue reactivity and craving on outcomes (r = 0.33, p < 0.001; approximately 11% of variance), suggesting that cue exposure and the experience of craving significantly influence and contribute to eating behavior and weight gain. Follow-up tests revealed a medium effect size for the effect of both tonic and cue-induced craving on eating behavior (r = 0.33). We did not find significant differences in effect sizes based on body mass index, age, or dietary restraint. However, we did find that visual food cues (e.g. pictures and videos) were associated with a similar effect size to real food exposure and a stronger effect size than olfactory cues. Overall, the present findings suggest that food cue reactivity, cue-induced craving and tonic craving systematically and prospectively predict food-related outcomes. These results have theoretical, methodological, public health and clinical implications.

Emotional eating and Pavlovian learning: does negative mood facilitate appetitive conditioning?

OBJECTIVE

Emotional eating has been suggested to be a learned behaviour; more specifically, classical conditioning processes might be involved in its development. In the present study we investigated whether a negative mood facilitates appetitive conditioning and whether trait impulsivity influences this process.

METHOD

After undergoing either a negative or neutral mood induction, participants were subjected to a differential classical conditioning procedure, using neutral stimuli and appetizing food. Two initially neutral distinctive vases with flowers were (CS+) or were not (CS-) paired with chocolate mousse intake. We measured participants' expectancy and desire to eat (4 CS+ and 4 CS- trials), salivation response, and actual food intake. The BIS-11 was administered to assess trait impulsivity.

RESULTS

In both mood conditions, participants showed a classically conditioned appetite. Unexpectedly, there was no evidence of facilitated appetitive learning in a negative mood with regard to expectancy, desire, salivation, or intake. However, immediately before the taste test, participants in the negative mood condition reported a stronger desire to eat in the CS+ compared to the CS- condition, while no such effect occurred in the neutral group. An effect of impulsivity was found with regard to food intake in the neutral mood condition: high-impulsive participants consumed less food when presented with the CS+ compared to the CS-, and also less than low-impulsive participants.

DISCUSSION

An alternative pathway to appetitive conditioning with regard to emotions is that it is not the neutral stimuli, but the emotions themselves that become conditioned stimuli and elicit appetitive responses.

A Bayesian hierarchical diffusion model decomposition of performance in Approach-Avoidance Tasks

Common methods for analysing response time (RT) tasks, frequently used across different disciplines of psychology, suffer from a number of limitations such as the failure to directly measure the underlying latent processes of interest and the inability to take into account the uncertainty associated with each individual's point estimate of performance. Here, we discuss a Bayesian hierarchical diffusion model and apply it to RT data. This model allows researchers to decompose performance into meaningful psychological processes and to account optimally for individual differences and commonalities, even with relatively sparse data. We highlight the advantages of the Bayesian hierarchical diffusion model decomposition by applying it to performance on Approach-Avoidance Tasks, widely used in the emotion and psychopathology literature. Model fits for two experimental data-sets demonstrate that the model performs well. The Bayesian hierarchical diffusion model overcomes important limitations of current analysis procedures and provides deeper insight in latent psychological processes of interest.

Analysis of blocking of flavor-preference conditioning based on nutrients and palatable tastes in rats

In Experiment 1 rats were given training in which a mixture of two flavors was paired with sucrose. This established a substantial preference for each of the flavors; however, when rats were given prior experience with just one of the flavors paired with sucrose, training with the compound produced only a weak preference for the other - an example of the blocking effect, well known in other associative learning paradigms. Both the palatable taste of sucrose and its nutrient properties contribute to its ability to reinforce preference acquisition. The role of these two forms of learning was examined in two further experiments in which the reinforcer used was fructose (which is considered to support preference learning because it is palatable but not through its nutrient properties) or maltodextrin (thought to support preference learning by way of its nutrient properties). In neither case was blocking observed. At the theoretical level, this outcome constitutes a challenge to the attempt to explain flavor-preference learning in terms of the standard principles of associative learning theory. Its implication at the level of application is that the potential of the blocking procedure as a technique for preventing the development of unwanted flavor preferences may be limited.

Individual variation in resisting temptation: implications for addiction

When exposed to the sights, sounds, smells and/or places that have been associated with rewards, such as food or drugs, some individuals have difficulty resisting the temptation to seek out and consume them. Others have less difficulty restraining themselves. Thus, Pavlovian reward cues may motivate maladaptive patterns of behavior to a greater extent in some individuals than in others. We are just beginning to understand the factors underlying individual differences in the extent to which reward cues acquire powerful motivational properties, and therefore, the ability to act as incentive stimuli. Here we review converging evidence from studies in both human and non-human animals suggesting that a subset of individuals are more "cue reactive", in that certain reward cues are more likely to attract these individuals to them and motivate actions to get them. We suggest that those individuals for whom Pavlovian reward cues become especially powerful incentives may be more vulnerable to impulse control disorders, such as binge eating and addiction.

The inertia of conditioned craving. Does context modulate the effect of counterconditioning?

Previous research (Van Gucht, Baeyens, Vansteenwegen, Hermans, & Beckers, 2010) showed that a cue, initially paired with chocolate consumption, did not cease to elicit craving for chocolate after extinction, but did so after counterconditioning (CC). CC moreover was more effective than extinction in changing evaluations, in disrupting reported cue-elicited expectancy to get to eat chocolate, and in reducing actual consumption. The present research aimed to investigate whether the advantage of CC over extinction in changing acquired craving and liking would survive a change in context after CC. One group of participants received acquisition, CC and a final test all in the same context A (AAA-COUNTER-group). A second group received CC in a different context B (ABA-COUNTER-group). To compare the degree of any renewal after CC to renewal after extinction, a third group received extinction rather than CC in context B (ABA-EXT-group). Data indicate that a context switch after CC/extinction (ABA-groups) results in a return of cue-elicited approach tendencies and US-expectancies that were reduced or reversed after CC/extinction (renewal). As before, acquired liking is reduced only through CC, not by an extinction procedure. After CC in a different context, a return to the original acquisition context did not renew liking.

Motivational Mechanisms and Outcome Expectancies Underlying the Approach Bias toward Addictive Substances

Human behavior can be paradoxical, in that actions can be initiated that are seemingly incongruent with an individual’s explicit desires. This is most commonly observed in drug addiction, where maladaptive behavior (i.e., drug seeking) appears to be compulsive, continuing at great personal cost. Approach biases toward addictive substances have been correlated with actual drug-use in a number of studies, suggesting that this measure can, in some cases, index everyday maladaptive tendencies. At present it is unclear whether this bias to drug cues is a Pavlovian conditioned approach response, a habitual response, the result of a Pavlovian-instrumental transfer process, or a goal-directed action in the sense that expectancy of the rewarding effects of drugs controls approach. We consider this question by combining the theoretical framework of associative learning with the available evidence from approach bias research. Although research investigating the relative contributions of these mechanisms to the approach bias is to date relatively limited, we review existing studies and also outline avenues for future research.

Quantifying individual variation in the propensity to attribute incentive salience to reward cues

If reward-associated cues acquire the properties of incentive stimuli they can come to powerfully control behavior, and potentially promote maladaptive behavior. Pavlovian incentive stimuli are defined as stimuli that have three fundamental properties: they are attractive, they are themselves desired, and they can spur instrumental actions. We have found, however, that there is considerable individual variation in the extent to which animals attribute Pavlovian incentive motivational properties ("incentive salience") to reward cues. The purpose of this paper was to develop criteria for identifying and classifying individuals based on their propensity to attribute incentive salience to reward cues. To do this, we conducted a meta-analysis of a large sample of rats (N = 1,878) subjected to a classic Pavlovian conditioning procedure. We then used the propensity of animals to approach a cue predictive of reward (one index of the extent to which the cue was attributed with incentive salience), to characterize two behavioral phenotypes in this population: animals that approached the cue ("sign-trackers") vs. others that approached the location of reward delivery ("goal-trackers"). This variation in Pavlovian approach behavior predicted other behavioral indices of the propensity to attribute incentive salience to reward cues. Thus, the procedures reported here should be useful for making comparisons across studies and for assessing individual variation in incentive salience attribution in small samples of the population, or even for classifying single animals.

Contextual control of appetite. Renewal of inhibited food-seeking behavior in sated rats after extinction

Obesity and overeating have become fundamental problems in modern society. This article studies the inhibition of food-seeking behavior, and how contextual cues can control it. Rats that had free food in the home cage nevertheless learned to lever press for sucrose or high-fat pellets in a distinctive context (a Skinner box). Lever pressing was then inhibited by extinction, in which lever presses no longer produced food. After extinction, inhibited responding was "renewed" when the rats were switched to a different context: in the new context, the rats lever-pressed again, and worked more for food when food was made available. These effects were observed when conditioning, extinction and testing occurred in contexts A, B, and A (respectively) or in A, A, and B. Thus, mere removal from the context in which food-seeking was inhibited initiated a return to food-seeking. The contextual control of extinction may help explain why food seeking and consumption seem so persistent.

Weight, gender, and snack appeal

In this study, we hypothesized that overweight/obese persons have an exaggerated approach tendency toward high calorie foods. Testing this hypothesis, a stimulus response compatibility (SRC) task was used to assess approach-avoidance tendencies toward food in both overweight/obese participants (n=42), and normal weight controls (n=46). The SRC task is a reaction time task measuring how fast one approaches and avoids pictures of food and non-foods according to given instructions. It was found that overweight/obese men are slower at avoiding particularly high calorie snack foods. But this does not appear to be the case for overweight/obese women who showed nearly as fast avoidance as approach toward the high calorie food cues. It is concluded that overweight/obese women, rather than men, are ambivalent toward high calorie foods, which is the likely result of high dietary restraint.